Pigeons may not remember the stimuli that reinforced their recent behavior.
Stimulus control can vanish while the reinforcing value of that stimulus hangs on.
01Research in Context
What this study did
Researchers tested pigeons on a delayed matching task. The birds first saw a color sample, then had to wait before picking the matching key.
Delays grew from 3 to 27 seconds. The team tracked two things: did the bird still peck (response rate) and did it pick the right color (accuracy).
What they found
After 3–9 seconds the pigeons’ accuracy fell to coin-flip level, yet they kept pecking hard until 15–27 seconds.
In plain words, the birds forgot which color paid off but still wanted the payoff.
How this fits with other research
THOMAS et al. (1963) showed pigeons can learn delayed matching only after they master zero-second delays. Donahoe et al. (2000) used that same setup to show the learned link fades fast.
Paul (1983) found ratio values themselves act like cues. The new study adds that cue strength can die while the reinforcing pull of the cue lives on.
Neuringer (1973) saw flat generalization after presence-absence training. Here, the “flat line” shows up as chance accuracy even when responding stays strong.
Why it matters
When you run delay tasks with kids, probe memory and motivation separately. A child may keep working for tokens yet have no idea which picture earned them. Slip in quick identity checks during long delays to be sure stimulus control is still there.
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02At a glance
03Original abstract
In two experiments the conditioned reinforcing and delayed discriminative stimulus functions of stimuli that signal delays to reinforcement were studied. Pigeons' pecks to a center key produced delayed-matching-to-sample trials according to a variable-interval 60-s (or 30-s in 1 pigeon) schedule (Experiment 1) or a multiple variable-interval 20-s variable-interval 120-s schedule (Experiment 2). The trials consisted of a 2-s illumination of one of two sample key colors followed by delays ranging across phases from 0.1 to 27.0 s followed in turn by the presentation of matching and nonmatching comparison stimuli on the side keys. Pecks to the key color that matched the sample were reinforced with 4-s access to grain. Under some conditions of Experiment 1, pecks to nonmatching comparison stimuli produced a 4-s blackout and the start of the next interval. Under other conditions of Experiment 1 and each condition of Experiment 2, pecks to nonmatching stimuli had no effect and trials ended only when pigeons pecked the other, matching stimulus and received food. The functions relating pretrial response rates to delays differed markedly from those relating matching-to-sample accuracy to delays. Specifically, response rates remained relatively high until the longest delays (15.0 to 27.0 s) were arranged, at which point they fell to low levels. Matching accuracy was high at short delays, but fell to chance at delays between 3.0 and 9.0 s. In Experiment 2, both matching accuracy and response rates remained high over a wider range of delays in the variable-interval 120-s component relative to the variable-interval 20-s component. The difference in matching accuracy between the components was not due to an increased tendency in the variable-interval 20-s component toward proactive interference following short intervals. Thus, under these experimental conditions the conditioned reinforcing and the delayed discriminative functions of the sample stimulus depended on the same variables (delay and variable-interval value), but were nevertheless dissociated.
Journal of the experimental analysis of behavior, 2000 · doi:10.1901/jeab.2000.73-125